The design of highly ordered supramolecular structures has attracted considerable interest in that the self-assembly of specifically tailored monomers possessing appropriate ligand directivity underpins the generation of novel and utilitarian supramolecular complexes with two- and three-dimensional nano- and macro-structures. Owing to their electronic and steric versatility, aromatic N-heterocycles continue to play a prominent role as classical ligands in coordination compounds, bridging ligands in binuclear derivatives, and building blocks for supramacromolecular assemblies. As a result of the connectivity of these polyheteroaromatics by transition metals, they also provide platforms for π-back-bonding and thus an opportunity for electron-delocalization and -transport as related to photon capture associated with light-energy conversion. More specifically, examples of self-assembled constructs have been reported based on the formation of stable transition metal complexes from tailored macromolecules. These types of transition metal complexes have also been applied to electroluminescence (EL) devices, since the fine tuning of the light-emitting properties can be achieved by structural modifications of the ligand or by using different transition metals. Light-emitting properties of some materials, which are composed of polymeric Rh(I) and Ru(II) bipyridine or Zn(II) terpyridine complexes, have also been reported.
One type of EL device is known as an organic light-emitting diode (OLED). An OLED is a thin-film light-emitting diode in which the emissive layer is an organic compound. OLED technology may be used to form picture elements in display devices. These devices could be much less costly to fabricate than traditional LCD displays. When the emissive electroluminescent layer is polymeric, varying amounts of OLEDs can be deposited in rows and columns on a screen using simple “printing” methods to create a graphical color display, for use as television screens, computer displays, portable system screens, and in advertising and information board applications to name a few.
An OLED works on the principle of electroluminescence. The key to the operation of an OLED is an organic luminophore. An exciton, which consists of a bound, excited electron and hole pair, is generated inside the emissive layer. When the exciton's electron and hole combine, a photon can be emitted. An exciton can be in one of two states, singlet or triplet. Only one in four excitons is a singlet. The materials currently employed in the emissive layer are typically fluorophors, which can only emit light when a singlet exciton forms, which reduces the OLED's efficiency. By incorporating transition metals into a small-molecule OLED, the triplet and singlet states can be mixed by spin-orbit coupling, which leads to emission from the triplet state.
It would be advantageous to provide a method of self-assembly of hexameric metallomacrocycles wherein the self-assembly process occurs by at least one metal-mediated moiety. It would also be advantageous to provide a method of self-assembly of hexameric metallomacrocycles, wherein the self-assembly process provides self-assembled structures having measurable photo- and electroluminescence properties and may be used in a light-emitting diode device.